A pediatric patient has mediastinal mass, lymphadenopathy, and peripheral blood shows lymphoblasts. Flow cytometry: TdT+, CD19+, CD10+, CD34+. Cytogenetics reveals a hyperdiploid karyotype (>50 chromosomes). What is the prognostic significance of this karyotype in B-ALL?
- A Favorable prognosis with excellent response to standard chemotherapy ✓
- B Poor prognosis requiring allogeneic stem cell transplant in first remission
- C Neutral prognosis; requires Philadelphia chromosome testing before risk stratification
- D Poor prognosis due to drug resistance conferred by extra chromosomes
Correct answer: A. Favorable prognosis with excellent response to standard chemotherapy
Explanation
Hyperdiploidy (>50 chromosomes, particularly gains of chromosomes 4, 10, 17, 21) in B-ALL is a favorable cytogenetic finding, associated with excellent event-free survival exceeding 85–90% with standard chemotherapy. The mechanism involves enhanced sensitivity to antimetabolites (methotrexate, mercaptopurine) due to increased uptake via additional copies of transporter genes. Hypodiploidy (<44 chromosomes) or t(9;22) (Philadelphia chromosome) confer poor prognosis requiring intensified treatment or SCT.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.